1. Field of the Invention
The present invention relates to a dehydration condition judging apparatus for judging if a dehydration condition is occurring by measuring bioelectric impedance of a living body.
2. Prior Art
Dehydration is a condition, in which water in a living body is abnormally reduced, and it often occurs in daily life when a person is exercising or when the temperature is high because a lot of water is excreted from the body by sweating and an elevated body temperature. Especially, it is said that elderly persons are apt to experience dehydration symptoms. This is because, when one becomes older, size of muscles which contain water decreases, the amount of urine increases because the function of the kidneys deteriorates, and awareness of thirsty decreases because the senses are dulled. Another reason is that the amount of water which cells require decreases.
If dehydration symptoms are left untreated, the dehydration symptoms will gradually become worse until a serious dehydration condition is occurring. Usually, it is said that, when one third of the water in a living body is lost, the body temperature regulation is disturbed. This causes the body temperature to increase, and then water in the living body is further reduced. In other words, vicious circle is created, until at last, a heat illness occurs. A heat illness includes conditions such as heat cramp, desert syndrome and heatstroke. Sometimes all the organs in the body are affected by the heat illness.
Thus it is desired that dehydration symptoms be dealt with at an early stage to avoid the risk of a heat illness. However, people are often not aware of dehydration symptoms at the early stage, and thus it is difficult for them to judge their dehydration condition in an early stage only based on self awareness. As a result, the dehydration symptoms are left untreated, which symptoms thus gradually becomes worse, until a subject finally feels dizzy or thirsty and thus realizes he/she is not in good condition. It often happens that he/she is actually in a serious dehydration condition at the time he/she feels dizzy.
Japanese Patent Laid-Open Publication No. Hei 11-318845 discloses an apparatus for measuring the total amount of water in a body, thus allowing dehydration symptoms which a person is not aware of to be detected. This apparatus determines the total amount of body water in a living body of a subject easily by measuring a bioelectrical impedance value.
However, in a case where this apparatus is used, dehydration symptoms can not be detected if a subject measures the total amount of body water spontaneously. The subject often forgets to measure the total amount of body water, and thus dehydration symptoms can not be detected at an early stage. Especially, as stated above, when a person is exercising or when the temperature is high, or in the case of an elderly person, dehydration symptoms are apt to occur. Thus, a person should pay special attention to the possibility of the development of dehydration symptoms. However, when a person is absorbed in exercising, he/she can not concentrate at such times because of the heat and humidity, and thus forgets to measure the total amount of body water. As regard to elderly people, they forget to measure the total amount of body water because they are not aware they are thirsty due to the dulling of their senses. As a result, it is difficult to detect dehydration symptoms at an early stage.
As above mentioned, a bioelectrical impedance value changes when the the total amount of body water changes. It is also known that a bioelectrical impedance value changes when the body temperature changes. That is, the bioelectrical impedance value decreases when the body temperature goes up, and the bioelectrical impedance value increases when the body temperature goes down. However, said conventional apparatus, calculating the total amount of body water based on the bioelectrical impedance value, does not take into consideration this fact that the bioelectrical impedance value changes when the body temperature changes. Thus, said apparatus can not determine the total amount of body water precisely, resulting in it being unable to judge the dehydration condition precisely. For example, in a case where the total amount of body water is decreased and the body temperature is raised, and thus a dehydration condition should be detected, the bioelectrical impedance value increases when the total amount of body water is decreased, while on the other hand, the bioelectrical impedance value decreases because body temperature is raised. Thus, when the bioelectrical impedance value is measured, and then the total amount of body water is calculated based on the bioelectrical impedance value to be able to determine whether a dehydration condition has occurred or not based on this calculated total amount of body water, the dehydration condition may not be detected.
Considering the above, an object of the present invention is to provide a dehydration condition judging apparatus which is capable of judging whether, with regard to a subject, a dehydration condition is occurring at appropriate times and without fail, and detecting a dehydration condition at an early stage accurately.
In one aspect of the invention, an apparatus for judging whether a dehydration condition is occurring (hereinafter a dehydration condition judging apparatus) comprises: a bioelectric impedance measuring device; a dehydration condition judging unit; an judgment result displaying unit; an inform time determining unit; and an informing device. Said bioelectric impedance measuring device supplies an alternating current to a body of a subject and measures a bioelectric impedance value; said dehydration condition judging unit judges a dehydration condition of the subject based on the measured bioelectric impedance value; said judgement result displaying unit displays the judged dehydration condition; said inform time determining unit determines an inform time; and said informing device informs the subject at the determined inform time that it is time to measure the total amount of body water.
In one embodiment of the invention, said bioelectric impedance measuring device supplies an alternating current of a single frequency. Alternatively, said bioelectric impedance measuring device supplies a plurality of alternating currents of different frequencies to the subject.
In another embodiment of the invention, the dehydration condition judging apparatus comprises a body temperature measuring device. Said body temperature measuring device measures a body temperature of the subject, and said dehydration condition judging unit takes into consideration the measured body temperature and then judges a dehydration condition of the subject based on the measured bioelectric impedance value.
In a further embodiment of the invention, the dehydration condition judging apparatus comprises an age inputting unit. Said age inputting unit has an age of a subject inputted into, said inform time determining unit then determining the inform time based on the inputted age.
In another embodiment of the invention, the dehydration condition judging apparatus comprises an action level input unit. Said action level input unit has an action level of the subject inputted into, said inform time determining unit then determining an inform time based on the inputted action level.
In another embodiment of the invention, the dehydration condition judging apparatus comprises a temperature measuring device. Said temperature measuring device measures a temperature, and said inform time determining unit then determines an inform time based on the measured temperature.
Said inform time determining unit determines the inform time based on any combination of the age of the subject, the action level and the temperature.
In another embodiment of the invention, said temperature measuring device measures the temperature again at least once in a period between the time the inform time is determined and the determined inform time, said inform time determining unit then determining another inform time again based on the temperature measured again.
In another embodiment of the invention, the dehydration condition judging apparatus comprises a humidity measuring device. Said inform time determining unit determines an inform time based on the measured temperature and humidity.